Electrostatic spray guns are useful in applying coatings with a high transfer efficiency. Such spray guns usually have a high voltage power supply located within the barrel of the gun which in turn typically contacts a metallic member to transfer voltage to the needle electrode.
Such spray guns have been sold by Graco Inc., the assignee of the instant invention under the trademark PRO GUN. That product had a spring which extended from the front end of the power supply and in turn contacted a conductive member within the barrel. Such a spring has either been in contact with the member directly or is contained within a rubber boot while contacting the member.
Such a construction, to a greater or lesser extent still allows some air to exist within the barrel of the gun in the presence of high voltage electric fields. The presence of this air can lead to the production of ozone which in turn can chemically attack the barrel of the gun and lead to electrical breakdown of the barrel.